# Licensed under a 3-clause BSD style license - see LICENSE.rst

from astropy import units as u
from astropy.utils.decorators import format_doc
from astropy.coordinates import representation as r
from astropy.coordinates.baseframe import BaseCoordinateFrame, RepresentationMapping, base_doc
from .galactic import Galactic

__all__ = ['Supergalactic']


doc_components = """
    sgl : `~astropy.coordinates.Angle`, optional, keyword-only
        The supergalactic longitude for this object (``sgb`` must also be given and
        ``representation`` must be None).
    sgb : `~astropy.coordinates.Angle`, optional, keyword-only
        The supergalactic latitude for this object (``sgl`` must also be given and
        ``representation`` must be None).
    distance : `~astropy.units.Quantity` ['speed'], optional, keyword-only
        The Distance for this object along the line-of-sight.

    pm_sgl_cossgb : `~astropy.units.Quantity` ['angular speed'], optional, keyword-only
        The proper motion in Right Ascension for this object (``pm_sgb`` must
        also be given).
    pm_sgb : `~astropy.units.Quantity` ['angular speed'], optional, keyword-only
        The proper motion in Declination for this object (``pm_sgl_cossgb`` must
        also be given).
    radial_velocity : `~astropy.units.Quantity` ['speed'], optional, keyword-only
        The radial velocity of this object.
"""


@format_doc(base_doc, components=doc_components, footer="")
class Supergalactic(BaseCoordinateFrame):
    """
    Supergalactic Coordinates
    (see Lahav et al. 2000, <https://ui.adsabs.harvard.edu/abs/2000MNRAS.312..166L>,
    and references therein).
    """

    frame_specific_representation_info = {
        r.SphericalRepresentation: [
            RepresentationMapping('lon', 'sgl'),
            RepresentationMapping('lat', 'sgb')
        ],
        r.CartesianRepresentation: [
            RepresentationMapping('x', 'sgx'),
            RepresentationMapping('y', 'sgy'),
            RepresentationMapping('z', 'sgz')
        ],
        r.CartesianDifferential: [
            RepresentationMapping('d_x', 'v_x', u.km/u.s),
            RepresentationMapping('d_y', 'v_y', u.km/u.s),
            RepresentationMapping('d_z', 'v_z', u.km/u.s)
        ],
    }

    default_representation = r.SphericalRepresentation
    default_differential = r.SphericalCosLatDifferential

    # North supergalactic pole in Galactic coordinates.
    # Needed for transformations to/from Galactic coordinates.
    _nsgp_gal = Galactic(l=47.37*u.degree, b=+6.32*u.degree)
